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Casey Pigge is shown in an undated photo provided by the Ohio Department of Rehabilitation and Correction. An investigative report by the Dayton Daily News has found that the strangulation of an inmate on an Ohio prison bus by Pigge, a twice convicted murderer, was preventable.

After Casey Pigge was taken into custody last year for using a brick to kill his cellmate by repeatedly smashing his head, he made one thing clear to investigators.

"Pigge denied any desire to be a serial killer, but could not promise that he wouldn't kill again," a prison social worker said after interviewing him.

He did kill again and was sentenced Wednesday to 25 years in prison.

On Feb. 1, just two days after pleading guilty to beating cellmate Luther Wade to death, Pigge was placed in a prison transport van with several other inmates.

As the bus headed south through Pickaway County in central Ohio, investigators say, Pigge used a chain meant to restrain him around the stomach to strangle inmate David Johnson — his second killing that week.

"I guess you never seen that on a bus before," Pigge boasted to the surviving inmates afterward, according to highway patrol records. Johnson was serving an eight-year sentence for sexual battery.

Pigge pleaded guilty Wednesday to killing Johnson and was immediately sentenced. The hearing took about three minutes.

Pigge apparently did not want to be around a sex offender, Pickaway County Prosecutor Judy Wolford said.

"Whether the gentleman that was killed was incarcerated or not, he was still a human being, and we still have a victim in this particular case," she said. "I'm pleased that justice has been served for him."

Pigge's attorney, Steve Larson, said he didn't discuss motives with his client.

"My position is, can they prove this case beyond a reasonable doubt. Obviously they could, he made statements against himself," Larson said.

Any time in prison for Johnson's death is moot: Pigge already is serving a life sentence for killing Wade and 30 years to life for fatally slitting the throat of his girlfriend's mother in 2008. He gave himself the nickname "box cutter" after the weapon he used to kill her.

The state prisons system has not said why Pigge, with his record, was placed in a van with the ability to carry out the killing of Johnson. The state updated its prison transportation policies afterward but won't release details.

"They definitely was not doing their job and monitoring us even with a known Hannibal Lecter with us," according to a letter from an inmate on the bus that day that was sent afterward to prisons director Gary Mohr, as reported by the Dayton Daily News.

Officers with the prisons' department SWAT unit transported Pigge Wednesday from the maximum Southern Ohio Correctional Facility in Lucasville. Three SWAT members were positioned in the courtroom and a fourth was just outside in the hall.

Pigge, 29, feared Wade was a member of the Aryan Brotherhood who planned to kill him, records show. He'd been Wade's cellmate at Lebanon Correctional Facility for one day when he talked him into being blindfolded as part of a card trick, then took a brick and brought it down again and again on Wade's head.

Even before Wade's killing, Pigge's prison misconduct record ran nearly 30 pages. Over the years, he repeatedly refused to enter his cell, was found with homemade alcohol, collected contraband like razor blades, electric cords and a TV converter box and fought other inmates.

Records show Pigge was born to a 14-year-old girl who used drugs and alcohol while pregnant with him. Child protection authorities first intervened when he was just 7 days old, according to a 2009 evaluation after Pigge killed his girlfriend's mother.

Pigge was burned with cigarettes as a toddler, forced as a child to urinate in a heating grate when his mother and stepfather locked him in a room, was possibly sexually abused, and was repeatedly abandoned, according to the report by psychologist Dennis Eshbaugh.

Pigge was placed in dozens of foster homes and hospitals over the years, and diagnosed with a mild mental disability. "In effect, the defendant is functionally a child in an adult body," Eshbaugh said.